Digital communication witnesses an evident and continuous development in several applications on the web. Hence, a secure communication session should be provided. The protection of information transmitted across a world network has become a key issue on the network performance measures. Cryptography and steganography are two necessary techniques that are wont to give network security. In this paper, we conduct a comparative study of steganography and cryptography. We survey a variety of ways combining cryptography and steganography techniques in one system. Moreover, we present a classification of those ways and compare them in terms of the formula used for cryptography, the steganography technique and also the file kind used for covering the knowledge.